In traditional hydraulic compositions for extrusion molding, asbestos were used as additive fibers for facilitating extrusion into hardened parts having surface smoothness. In the recent years, the amount of asbestos used drastically decreased due to health considerations and legal regulations. At present, pulp fibers are often used as the substitute. In unison with this tendency, nonionic water-soluble cellulose ether is commonly used for the purposes of improving the dispersion of pulp fibers, enhancing strength properties and facilitating extrusion.
As the avoidance of asbestos is in progress, the amount of nonionic water-soluble cellulose ether used is increasing. This increases the cost of extruded parts, preventing widespread use thereof.
Extrudability depends on the solubility of a nonionic water-soluble cellulose ether used. On use of a nonionic water-soluble cellulose ether having a slow dissolution rate, a longer time of kneading is needed or the amount of the cellulose ether must be increased. These drawbacks also increase the cost of extruded parts, preventing widespread use thereof.